Bioactive Compounds and Antioxidant Activities of Thyme-Enriched Refined Corn Oil

This study was designed to examine bioactive compounds of the thyme-enriched corn oil and to determine the antioxidant activity of its methanolic extract. Volatile compounds composition was investigated by Gas Chromatography-Mass Spectrometry (GC-MS), whereas phenolic compounds analysis was performed by Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC). Antioxidant activities of the flavoured oil methanolic extract were evaluated using DPPH radical scavenging, β-carotene-linoleic acid bleaching, reducing power and total antioxidant assays. Flavoured oil major volatiles were p-cymene (۲۶.۴۷%), α-thujene (۲۴.۰۶%) and γ-terpinene (۱۴.۳۰%). Its methanolic extract had higher Total Phenol Contents (TPCs) (۵۳.۹۹ mg ۱۰۰ g-۱) than that of the crude oil (۲۳.۶۳ mg ۱۰۰ g-۱). Thymol was the main phenolic compound in the flavoured oil (۵۵.۸۴%). Flavoured oil methanolic extract showed higher total antioxidant activity (۱۸۵.۲۲ mg Gallic Acid Equivalent (GAE) ۱۰۰ g-۱) than that of the crude one (۱۰۰.۶۶ mg GAE ۱۰۰ g-۱). In β-carotene-linoleic acid bleaching and DPPH radical scavenging assays, flavoured oil methanolic extract showed higher activities than that of the crude oil based on IC۵۰values. Flavoured and crude oils were characterized by a close CE۵۰values (۱.۸۱ and ۱.۸۵ mg mL-۱, respectively). Antioxidant activities of the thyme-enriched oil were mainly due to the presence of phenolic compounds such as thymol and hydrocarbons such as γ-terpinene and p- cymene. The thyme-enriched oil could be considered as a new and natural source of antioxidant.

Keywords:

Antioxidant activity , Corn oil , Essential oil , Polyphenols , Thymus capitatus